Various sensor systems have been developed for detecting sheet properties “on-line,” i.e., on a sheet-making machine while it is operating. Sensors for continuous flat sheet production processes typically employ single or dual-sided packages with on-line sensors that traverse or scan traveling webs of sheet material during manufacture. With dual scanners, the heads or assemblies are fixed to beams of a scanner frame system that span both sides of the sheet with linear guidance tracks to allow the sensors to move in unison in the cross direction, i.e., in the direction perpendicular to the direction of sheet travel. Depending upon the sheet-making operation, cross-directional distances can range up to about twelve meters or more. In the paper making art, for instance, the on-line sensors detect variables such as basis weight, moisture content, and caliper of sheets during manufacture. There is a desire to provide a method of monitoring the operating condition of the scanner frame system in order to provide early warning of component failure, contaminant buildup, or other detrimental operation conditions. Scanner heads are equipped with alignment or head displacement sensors that provide differential head displacement readings. However, such readings do not disclose the source of the misalignment. The main obstacle is that the potential failure modes are numerous with even more causes to those failure modes and therefore instrumenting a scanning frame for each individual cause is resource prohibitive.